82 HEREDITY [CH. 



In Chinese Primulas a curious case of inter- 

 relation between flower-colour and structure has 

 been investigated by Bateson and Gregory. They 

 find that the long-styled and short-styled types of 

 flowers, so well known from Darwin's work, are an 

 allelomorphic pair, short-styled being dominant. But 

 when the long-styled factor is associated with a con- 

 dition in which the yellow eye of the flower is enlarged 

 to cover about half the area of the petals, the style 

 remains short, although the anthers occupy the typical 

 long-styled position in the tube of the flower. This con- 

 dition is called 'homostyle' (fig. 10 C, p. 81). When a 

 short-styled small-eyed plant iscrossed with homostyle 

 large-eyed, all the (F^) offspring are short-styled and 

 small-eyed, these characters being dominant. But in 

 the second generation, (F 9 ), obtained by breeding to- 

 gether these Fi plants, the following types appear : 



9 short-style with small eye, 

 3 short-style with large eye, 

 3 long-style with small eye, 

 1 homostyle with large eye. 



The long-styled form has appeared in .F 2 from short- 

 style x homostyle, because homostyle is a condition 

 of long-style modified by association with the large 

 eye. When this association is broken, the long-style 

 appears. 



From these examples of the interaction of distinct 



